Rescuers search the site of a recent plane crash in Tengxian County, south China's Guangxi Zhuang Autonomous Region, March 28, 2022. Search work at the site of the recent plane crash in south China is continuing after the second black box was found on Sunday, an official said at a press briefing on Monday afternoon.(Photo: Xinhua)

China's civil aviation regulator on Wednesday released the preliminary report on the tragic crash of China Eastern flight MU5735, saying that the investigation so far found "no abnormality" in aircraft maintenance or airline personnel. 

The Civil Aviation Administration of China (CAAC) also said that the qualifications of the crew members and maintenance personnel on duty met the requirements, the plane's airworthiness certificate was valid, and there were no abnormalities in navigation and surveillance equipment along the route or dangerous weather conditions. 

Before deviating from cruising altitude, radio communications between the crew and air traffic control were normal, the CAAC added. 

The CAAC's preliminary report said the two recorders on the plane were severely damaged due to the impact, and the data restoration and analysis work is still in progress. 

The technical investigation team will continue to carry out in-depth investigation of the accident cause, the CAAC said. 

The fatal crash on March 21 killed all 132 people onboard.

A preliminary investigation report in English and Chinese is required to be submitted to the International Civil Aviation Organization within 30 days after a plane crash, according to industry regulations.

Unlike the final investigation report, the contents of a preliminary report are the factual information collected by the investigators, including the flight history, radar information and weather information, said Qiao Shanxun, secretary general of the Expert Committee of Henan Aviation Industry Association.

The preliminary report does not include the reason of the air crash, he noted.

Market insider Hangkong Wuyu, an aviation blogger with more than 6.3 million followers on Twitter-like Sina Weibo, agreed. 

This report usually only states known facts and does not involve other content that needs to be investigated and verified, the blogger said.   

The accident investigation is inseparable from professional operations such as interpretation of the black box, on-site investigation, recovery of wreckage, visits to personnel and units, and laboratory testing. This is a very rigorous and meticulous process, and it will not be that fast, he said.

The CAAC's preliminary report said the two recorders on the plane were severely damaged due to the impact, and the data restoration and analysis work is still in progress. The technical investigation team will continue to carry out in-depth investigation of the accident cause. 

Earlier, online speculation swirled that the co-pilot "might be responsible" for the crash, claiming the black box data had been disclosed, with some believing that the CAAC will require flight crews to undergo mental health monitoring. 

On April 11, the CAAC refuted rumors surrounding the plane crash, saying the tragic accident is still under investigation, and no conclusions have been drawn on the cause and nature of the accident yet.

Qiao earlier told the Global Times that there were 1,157 accidents between 1990 and 2016, but only 62 percent of the crashes resulted in the release of final investigation reports, citing data from the ICAO.

The Chinese civil aviation regulator said in early April the industry must engage in deep reflection over the recent crash, and it vowed to ensure the safety of aviation operations and public safety.

It said that the industry should strengthen training and qualification management of key professional positions such as flight crew, air traffic control staff and maintenance workers, and those small carriers and airports that have not yet achieved best practices are also a key focus for ensuring safety.